//讀取配置文件（屬性文件）的工具類
public class ConfigManager {
 private static ConfigManager configManager;
 // properties.load(inputStream);讀取屬性文件
 private static Properties properties;

 // 在構(gòu)造工具類時(shí)，進(jìn)行配置文件的讀取
 private ConfigManager() {
  String configFile = "database.properties";
  properties = new Properties();
  InputStream is = ConfigManager.class.getClassLoader()
    .getResourceAsStream(configFile);
  try {
   // 讀取配置文件
   properties.load(is);
   is.close();
  } catch (IOException e) {
   e.printStackTrace();
  }
 }

 // 通過單例模式設(shè)置實(shí)例化個(gè)數(shù)
 public static ConfigManager getInstance() {
  if (configManager == null) {
   configManager = new ConfigManager();
  }
  return configManager;
 }

 // 通過key獲取對(duì)應(yīng)的value
 public String getString(String key) {
  return properties.getProperty(key);
 }
}

import com.book.util.ConfigManager;

//基類：數(shù)據(jù)庫操作通用類
public class BaseDao {
 protected Connection conn;
 protected PreparedStatement ps;
 protected Statement stmt;
 protected ResultSet rs;

 // 獲取數(shù)據(jù)庫連接
 public boolean getConnection() {
  // // 讀取配置信息
  String driver = ConfigManager.getInstance().getString(
    "jdbc.driver_class");
  String url = ConfigManager.getInstance().getString(
    "jdbc.connection.url");
  String username = ConfigManager.getInstance().getString(
    "jdbc.connection.username");
  String password = ConfigManager.getInstance().getString(
    "jdbc.connection.password");
  // 加載JDBC驅(qū)動(dòng)
  try {
   Class.forName(driver);
   // 與數(shù)據(jù)庫建立連接
   conn = DriverManager.getConnection(url, username, password);
  } catch (ClassNotFoundException e) {
   return false;
  } catch (SQLException e) {
   return false;
  }
  return true;
 }

 // 增刪改的通用方法
 public int executeUpdate(String sql, Object[] params) {
  int updateRows = 0;
  getConnection();
  try {
   ps = conn.prepareStatement(sql);
   // 填充占位符
   for (int i = 0; i < params.length; i++) {
    ps.setObject(i + 1, params[i]);
    System.out.println(i + 1 + "---" + params[i]);
   }
   System.out.println(sql);
   updateRows = ps.executeUpdate();
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return updateRows;

 }

 // 查詢
 public ResultSet executeSQL(String sql, Object[] params) {
  getConnection();
  try {
   ps = conn.prepareStatement(sql);

   // 填充占位符
   for (int i = 0; i < params.length; i++) {
    ps.setObject(i + 1, params[i]);
   }
   rs = ps.executeQuery();
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return rs;

 }

 // 關(guān)閉資源
 public void closeAll(){
  try {
   if(rs!=null){
    rs.close();
   }
   if(stmt!=null){
    stmt.close();
   }
   if(ps!=null){
    ps.close();
   }
   if(conn!=null){
    conn.close();
   }
  } catch (SQLException e) {
   e.printStackTrace();
  }
 }
}